An archaeological discovery of 13 Conehead-shaped skulls in Mexico has people recalling the famed Saturday Night Live sketch. The bones, which are about 1,000 years old, dating back to 945 A.D. to 1308 A.D., were discovered accidentally during a dig for an irrigation system in the northwest state of Sonora in Mexico. While it’s not unheard of for archaeological sites to be unearthed during modern excavations, the misshapen skulls discovered on the site are fairly uncommon, especially as far north as Sonora. “This was a Hispanic cemetery with 25 skulls, and 13 of them have deformed heads,” Cristina Garcia Moreno, who worked on the project with Arizona State University, told ABC News. “We don’t know why this population specifically deformed their heads.”

While the site, known as El Cementerio, was discovered in 1999, Moreno and her colleagues completed their analysis of the skeletal remains just last month. They plan to continue their research during the next field season. Discovered on the site were artifacts like pendants, nose rings and jewelry along with the remains of 25 people, 13 of whom had skulls deformed into an alien-looking cone shape. The deformation of human skulls was part of an ancient ritual practiced some 1,000 years ago in that area; it was achieved by binding a person’s head between two blocks of wood to apply pressure on the skull. “Cranial deformation has been used by different societies in the world as a ritual practice, or for distinction of status within a group or to distinguish between social groups,” said Moreno, adding, “The reason why these individuals at El Cementerio deformed their skulls is still unknown.”

Many of the bones were the remains of children, which led Moreno to believe that the practice of deforming skulls “may have been inept and dangerous.” The practice of artificial skull deformation was not limited to Mexico, though. The Chinookan tribes of the U.S. Northwest and the Choctaw of the U.S. Southeast both practiced the ritual.